In the field of flexographic printing ink samples are obtained by drawing ink over a substrate using a hand ink proofer of the type manufactured by Harper Companies International of Charlotte, N.C. The ink is applied to the substrate by manually rolling the hand proofer across the substrate. Manual ink proofer tools are utilized for proofing ink colors in order to accurately predict the results to be obtained by running a selected ink specimen in a printing press. A computer microscope is then used to view the ink smear on the substrate. The computer then indicates to the operator various color components to be added to the ink in order to achieve the desired ink coloration.
In a flexographic printing operation, rubber plates are utilized for delivering the ink to the stock or paper to be printed. A flexographic ink technician is usually given an ink specimen which has been determined to be acceptable for use on a particular press, and a production run sample, to be used as the standard for color and density. One of the most difficult tasks facing a flexographic ink technician is proofing an ink in a manner so that the color will duplicate the color of the production run sample from the flexographic printing press. It is well known among those skilled in the art that if three trained technicians pull an ink proof, using the same ink on the same hand proofer tool, three different color shades will result.
Color shade on a flexographic printing press is dependent on the ink film thickness applied to the substrate or stock. The ink film thickness is determined by the speed of the press, the pressure applied between the printing plate and paper (i.e., impression), and the pressure between the rollers on the printing unit. Similarly, color shade on a flexographic hand proofer tool is also dependent on the ink film thickness applied to the substrate which thickness is determined by the speed at which the technician pulls the hand proofer across the substrate, and the impression pressure the technician applies to the hand proofer while moving it across the substrate. Thus, the speed and impression is totally dependent on the manual skill of the flexographic ink technician, while the only variable not controlled by the technician is the pressure between the ink roller and transfer roller of the manual proofer tool.
U.S. Pat. No. 6,814,001 describes an ink proofer designed to overcome the problems associated with conventional manual proofer tools by generating consistent and reliable ink draws using a hand-held proofer tool retained in a movable mounting assembly. A variable pressure system is coupled to the mounting assembly to move the proofer tool into a contact position with a cylindrical drum. The transfer roller of the proofer tool then transfers ink to a substrate inserted between the drum and the transfer roller of the proofer tool when a drive motor for the drum is engaged.
While the ink proofer described in U.S. Pat. No. 6,814,001 shows a support roll for supporting a roll of substrate, the cylinder drum is the only mechanism that moves the substrate through the ink proofing arrangement. This limits some of the types of proofs that can be created as compared to the flexibility of hand proofing tool in terms of the relative movement of the proofing tool and the substrate.
Accordingly, there is a need for an ink proofer arrangement that provides a reliable, consistent and repeatable ink proof on a substrate, irrespective of the experience of the ink technician producing the ink proof. Additionally, there is a need for an ink proofer arrangement that permits a flexographic ink technician to more efficiently create proofs that involve differing tensions of the substrate and the hand proofing tool. An approach that addresses the aforementioned problems, as well as other related problems, is therefore desirable.